Method of drying hides and skins



Aug. 8, 1939. w. HYDE ET AL 2,168,478

I METHOD OF DRYING HIDES AND SKINS Fil ed Oct. 14, 195'! z sheets-shawlFigtl.

, Air Temp era ture 40 4% 5'0 5 Relative Hllfilldl ty g 0% *2 E 150. v 450-- w a g 100 T 40 I ,2 a 2 50 V v 1 30 3 FE 0' g WVE/VTME H. W. HYDEET AL METHOD OF DRYING mums AND sxms Aug. 8, 1939.

2 Sheets-Sheet 2 Filed Oct. 14, 1937 TUQE Patented Aug. 8, 1939 PATENTiFFiC 2,163,473 METHOD OF DRYINGHIDES AYD SKINS Henry W. Hyde, Dedhani,and David Edgar,

Lynn, Mass, assignors to The Tanning Process Company, Boston, Mass,aeorporation of Massachusetts Application October 14 1937, Serial No."168,928 7 11 Claims.

This invention relates to methods of drying hides and skins. While. theinvention; is illustrated with reference to the drying of chrome tannedskins in slicked-out condition on suitable supports, it is to beunderstood that the. invention and various important characteristicsthereof may have other applications and uses.

It is an object of the invention to facilitate the drying of'hides andskins in such manner as to minimize the amount of time required in thedrying operation, thereby increasing the output of a given'drying unit.It is a further object of the' invention to produce a better product inthe drying of hides and skins, whereby they emerge from the drier in animproved, relatively soft and plump condition. i

It is an important characteristic of the invention that, at the outsetof drying operations upon hides or skins, they are subjected totreatment by air circulating at high temperatures'of the order of 212Fland over, to raise the temperature of the hides or skins and of thewatery contents thereof to a high-degree in minimum time, therebygreatly facilitating evaporation, as a preliminary to other treatment bycooler air to complete the drying operation. Preferably the hides orskins are initially treated by air circulating at about 250 F. and arethen subjected to 'airof gradually-decreasing temperature and lower relative humidity to complete the drying operations. Hides and skins difierfrom all other sheet ma.- terial in that the middle back portionsthereof are relatively thicker and denser in structure than theloosertextured belly, flank, and shank portions. It is clear then thatthe last-named portions of each-hide or skin will dry much more readilythan other portions and may even become dry and hard'while the backportions are still moist.' Accordingly, it is contemplated to give theback portions of each hide or skin a preliminary heat treatmentsubstantially greater in extent than other portions of these same hidesor skins. To this end, currents of air at temperatures within therangepof about 212 litto about 250 F. are'directed along these backportions from one end of the skin to the other, thus quickly raising thetemperature of these parts" and thus facilitating drying operations. Itis to be understood that'all the other portions of each hide orskin geta substantial heat treatment simultaneously with the specialtreatment-of the back portions. However, the main currents of air arepreliminarily restricted to the back portionsof each hide or skin toraise. these portions to a high temperature in minimum time, Preferably.air currents at high temperature, flowing parallel to the backbone lineof each hide or skin,

. are caused to move alternately in opposite directions, 1. e., fromneck to butt and fromi butt to neck, thus tending to secure morecomplete unineck, thus'tending to secure more complete uniformity in theheating and drying efiects of the air currents.

These and other importantcharacteristics of the invention will now bedescribed in detail in the specification and then pointed out in theappended claims.

The invention is illustrated with reference to a drier and to chartsshown inthe accompanying drawings, in which r Fig. 1 is a chartindicating the relationship of air temperature and relative humidityduring drying operations on hides or skins in. accordance with themethod herein described;

Fig. 2 is another form of chart which indicates relationship oftemperature and relative humidity in successive compartments of a drierutilizedin the practice of the method;

Fig. 3 is a sectional view taken along the line III-III of Fig. 5showing the location and direction of air currents with respect to askinslicked out on a board;

Fig. 4 is a view similar to Fig. 3 taken along the section line IV-IV ofFig.5; l

Fig, 5. is a more or less diagrammatic top plan view of a drier whichmay be utilized. inthe practice of the method; and u r 1 I Fig. 6 is avertical longitudinal sectional view taken along the linelZlE-JII ofFig. 5 and lookinginthe direction of the arrows.

In the illustrated apparatus, which is designed specially to practiceour improved method of drying hides and skins, there is providedarelatively long chamber made up of communicating compartments t, ii,til, it, Hi, E6, l8 and :20, in line with each other. 'i'ravelingthrough all of these compartments is a conveyor mechanism comprising anupper endless conveyor 22 and a similar endless conveyor't t at thebottom of the chamber, As shown. most clearly in Fig. 6, each conveyoris provided irvith trough-like carriers 26 tohold the sheet materialtobe dried. Conveniently these carriers 26 are metal members extendingacross and connecting endless link chains 28 (Figs. 5 and 6)whici'i'pass around sprocket wheels at each end of the chamber, one ofthe sprocket wheels being shown at 30 in Fig. 6. It will be understoodthat-the chains 28 are suitably supported between their end sprockets inaccordance with well-known practice.

Upon inspection 'of Fig. 6, it will be clear that a trough-shapedcarrier 20 upon the upper run of the lower conveyor 24 is in verticalalinement with a trough-shaped carrier 26 on the lower run of the upperconveyor 22 so that a board I! may be slid endwise into the carriers IIand be held firmly in vertical position for travel through the drierchamber. The boards 32v may be of any well-known construction and areeach adapted to have a hide or skin slicked out thereon and attachedthereto before the said board is introduced into the drying chamber.Each board may have a skin slicked out on each side thereof.Alternatiyely each board may carry only one skin in which case twoboards will be placed back to back in each pair of upper and lowercarriers II. It will be readily understood that the boards with the workpieces thereon are introduced at the left end of the drier chamber(Figs. 5 and 6) and are removed at the right end of the'drier chamber asthey are presented at the latter end progressively with the travel ofthe conveyor mechanism through said drier chamber. At theend of thisjourney through the drier chamber, the hides or skins are in asatisfactorily dried condition. Hence, when the boards are removed fromthe chamber they are first separated from the dried hides or skins andare then returned to a station adjacent to the entrance end of'thechamber where other hides or skins may be atddtached to the said boardsfor a trip through the Upon reference to the charts shown in Figs. 1 and2, the relationship and range of air temperatures and of relativehumidity throughout the drying operation will be found clearly indicatedIt is to be understood that the range of air temperature and relativehumidity may be varied somewhat from that indicated without departingfrom the substance of the invention.

Shortly after their introduction into the conveyor mechanism, the skinsenter the first compartment i where the drying operation begins. Asshown most clearly in Fig. 3, air is circulated through this compartmentin a direction such that the heated air travels from one end to theother of the skin in an upward direction and substantially parallel tothe backbone line of the skin. Preferably, and as shown, the inlet andoutlet openings l0, 42, respectively, are so constructed and arrangedthat the air currents are restricted mainly to those portions of eachskin adjacent to, the backbone line thereof, the purpose being to supplyin abundance heated air to the denser and thicker portions of each skin,as distinguished from the thinner and more loosely textured portions ofthe belly, flanks, and shanks of these same skins. It will beunderstood, of curse,.that all of compartment 6 is heated by the hot aircirculated therethrough. However,

the velocity of the air currents is much greater along and over theheavier portions of each skin where it is more difficult to heat and toevaporate the moisture. The treatment in this compartment lasts abouteighteen or-twenty minutes. I

For circulating the air through the compartment 6 at a velocity of about2000 feet per minute there are provided two-or more blowers indicated atH which direct the air through heating units conveniently shown aselectric resistance units as indicated at 46, although steam pipes maybe used if desired. By the use of-adequate-equipment, as shown, the airin the compartment 8 is readily maintained at a temperature of aboutmeans 250 F. Since the; skins have been freshly slicked out upon theboards 32 just before the introduction of the latter into thecompartment 6, there is a substantial amount of liquid ready to bevaporized by the hot air currents which sweep through the compartment inthe manner described. Accordingly, it is found that the relativehumidity of the circulating air remains pretty constantly at about 56%.

As the conveyor mechanism moves the work pieces slowly through thecompartment 6 the skins are quickly heated to a high temperature. Thisis not only true of the hide or skin substance but of their waterycontents. This condition favors evaporation to a marked degree. While asubstantial amount of evaporation takes place, the amount of which maybe controlled by admitting outside drier air into the compartment 5, the

main purpose is to bring the hides or skins and the watery contentthereof quickly to a high temperature in a minimum time, therebycontributing greatly to the rapidity 'of drying operations in succeedingcompartments.

As the skins on their supporting boards 32 pass into compartment 8, theyare subjected to very much the same conditions as in compartment 0 withthe exception that the air currents are traveling in the oppositedirection from end to end of each skin, thus tending to make uniform thetreatment of all those thicker denser portions lying along each side ofthe backbone line of each skin. If the boards 32 be placed in theconveyor mechanism with the neck portion up, as indicated in Figs. 3 and4, the air currents in the first compartment 8 are passing from butt toneck, there being thus a tendency to remove more moisture from the buttend of the skin than from the neck end thereof. However, any tendency tonon-uniiormity in this respect is corrected in compartment 8 (Fig. 4)wherein the air currents are directed from neck to butt. In thiscompartment, blowers 48 are provided at the top of the compartment toblow air through electrical heating units 50 to heat the air whichpasses through inlet and outlet openings i2, 5!, respectively, so as torestrict the air currents very largely to the backbone portions of theskins. Inasmuch as more outside (or drier) air is admitted into thecompartment 8, the temperature thereof is somewhat lower than thecorresponding air inv compartment 6, being about 248 F. with a relativehumidity of about 52%. While substantial evaporation is taking place incompartment 8 it is still a main characteristic of the operation thatthe hides or skins are being heated to a relatively high temperature.The treatment in this compartment lasts about eighteen or twentyminutes. From then on, the temperatures in the various compartments dropsubstantial amounts from compartment to compartment as the dryingprogresses.

/ Upon inspection of Figs. 5 and 6, it will be observed that the aircurrent through compartments lll, l2, ll, l6 and I0 is directedalternately upwardly and downwardly of the skins on the drying boards,and that the direction of the air current is from'a compartment II,where the skins are drier, to other compartments where the skins arerelatively more moist. As shown, air currents enter the compartment i8from a blower compartment 56 (Fig. 5), pass upwardly through the bottomthereof and spread out to pass over the whole surface of each skin, itbeing understood that the vertically positioned drying boards 33 direct'the air upwardly through the spaces between the said boards and that theair is free then to pass from an enclosure at the top of the chamber 18-through an opening 60 (Fig. 6) into the top of the' compartment 16, theair being forced to move downwardly-through the spaces between theboards 32 in said compartment since there is a wall 62 between theenclosure at the top of compartment l6 and the enclosure at the top ofcompartment 14. From the bottom of thecompartment It the air currentspass through an opening at 54 into the bottom of the compartment H.Because of a wall located at 65, the air currents must now pass upwardlybetween drying boards in the compartment M to an enclosure at the top ofsaid compartment from which the air escapes through an opening 66 intothe enclosure at the top of the compartment 12. Here, again, because ofa wall 68, the air must pass in a downward direction through thecompartment 12, thence through an opening 10 into an enclosure (havingan end wall 1|) at the bottom of the compartment l0, through which itpasse's in anupmaintained at a temperature of about 210 the relativehumiditybeing about 48%; The air temperature becomes gradually less asthe hides or skins travel along the drier chamber, the temperature incompartment l2 being about 198 F., I

in compartment it about 195 F., in compartment I6 about 180 F., and incompartment 18 about 162 F. Theamount ofmoisture in the air is graduallydecreasing at the same time, as shown by the fact that the relativehumidity in compartment i is 48% while in compartment I0 it is about35%; While the construction is such that air is recirculated through thecompartments to H1, inclusive, it is to be understood that openings areprovided in the side walls of the compartments withsuitable covers 84,which may be readily manipulated by the worker to permit introduction ofoutside air as a measure of control of both humidity and temperature, itbeing understood further that suitable recording instruments for bothhumidity and temperature may be providedfor each compartment. Air, forthe last compartment 20 enters the top of the compartment from a blowerbox 85 (Fig. 5) and passes downwardly in the spaces between the dryingboards, and out into the room. This air reaches the compartment 20through a conduit 06 which takes warm air from the top of the room inwhich the drier is located, provision being also made to take some orall of the air from out-of -doors, depending upon the temperature andthe relative humidity of the out-door air. The average temperature ofthe compartment 20 is about 72 F. and the relative humidity a littleover 30%. This means that the air is quite dry and that the temperatureis low compared with the range of temperatures in the precedingcompartments. This seems to be a decided advantage since it causes theleather to come out soft and plump.

It will be noted that, in the foregoing description, temperatures of thecirculating air. only have been given as indicating the heat treatmentfat the end of the first two compartments.

of the skins in thevarious compartments of the drier chamber. However,these air temperatures give littleor no indication of the temperature ofthe skins in these various compartments. Whereas. the air temperature inthe first compartment isv approximately 250 F.,* the skin which hastraveled almost through this compartment and is about to leave it forthe next compartmentis found to have atemperature of 142 F. in itsbottom center portion, 134 F. in its top center portion, with about 116F. in the fianksl Since these skins atthe time of entering the drierchamber were at room temperature (about 80 F.) it will be seen that thetemperature of the skin and its watery content was raised very promptlythrough treatment by air circulating at 250 F. This same skin at the endof its travel through the next compartment 8,-

wherein it received treatment by air circulating at 245 F.,.had reacheda temperatureof 148 F. at both top and bottom centers, with atemperature of 124 -F in the flanks.v While the temperature of thecirculating air in the third compartment l0 drops to about 210 F., thetemperature of the skin at the end of this compartment was up to 149 F.in both top and bottom centers, with the flanks at 136 F. In the fourthcompartment It? with air circulating at about 200 F., the temperature ofthe skin-in top and bottom centers was 148. F. with the flanks at 144 F.

The temperaturesof the skin in the fifth and sixth compartments l4 and16 were substantially-those of the skin inthe fourth compartment whilein the seventh compartment l8 where the temperature of the air is about160 the skin has a'temperature of 148 F. in all portions thereofincluding the flanks. At the end of the drier, i. e., at the end ofcompartment 20, the skin had a temperature of 98 F. in all portions. Thefigures given as skin temperatures are approximate only because of thedifliculties in getting the skin temperature through manipulation of,the thermometers and of the skin portions which had to be lifted fromthe board. Still it is believed that the temperatures given above arenot more than three or four degrees below actual temperatures of theskins in the different compartments and that the data thus securedreflects accurately the range of temperatures of the skins throughoutthe illustrated drier. It is to be noted that, whereas theairtemperatures were relatively very high, reaching 250 F., the skins atno time exceeded a temperature of about 150 F. For chrome-tanned skinsthis is an entirely safe temperature, in fact substantially belowthe"temperature that might. be applied with safety, since chrome-tannedskins will stand much higher temperatures than skins tanned with anyother tanning material. It is to be noted also that while air wascirculated through the first two compartments at over 245 and while theair temperature was progressively lowered in the succeedingcompartments, still the skins maintained substantially the sametemperature throughout the third, fourth, fifth, sixth and seventhcompartments as that attained The explanation of the fact that theskinsat no time exceeded a temperature of about 150 F. is that the occurrenceof evaporation helped to keep the temperatures of the skins much lowerthan that indicated for the circulating air. In other words, while theskins were being heated to high temperatures in minimum time in thefirst two compartments, they were also being subjected to verysubstantial evaporation of their watery contents. It is therefore amatter of importance that skins subjected to air at very hightemperatures in drying operations should have a substantial waterycontent to begin with or that the highly heated air should have highrelative humidity to eflect quick drying without damage to the tannedskins.

The length of the chamber and the speed of the conveyor mechanism issuch that a hide or skin entering the inlet end of the drier'chamberappears at the outlet end in about two and onehalf hours.

Having described our invention, what we claim as new and desire tosecureby Letters Patent of the .United States is:

1. That improvement in methods of drying mineral tanned hides and skins,which comprises subjecting each hide or skin to currents of air attemperatures around 250 F. to heat such hide or skin and the waterycontents thereof to a high temperature in minimum time, therebyprovidingconditions which favor and eflect rapid evaporation 01' the water in thehide or skin, and subsequently subjecting these same hides and skins toair oi gradually decreasing temperature and lower relative humidity tocomplete the drying operation.

2. That improvement in the methods of drying mineral tanned hides andskins, which comprises subjecting the thicker denser middle backportions of each hide or skin to currents of air at temperatures ofabout 250 F. to heat such portions and the watery contents thereof to ahigh temperature in minimum time, and subsequently sub= jecting allportions of these same hides and skins to air oi gradually decreasingtemperature and lower relative humidity to complete the dryingoperation.

3. That improvement in methods of drying mineral tanned hides and skinswhich comprises subjecting each hide or skin to air at temperatures inthe range between about 245 F. and about 250 F. for about 40 minutes andsubsequently subjecting the same hide or skin to air currents oftemperatures ranging from about 180 F. gradually down to about F. with'agradual decrease in relative humidity to about 30% to eii'ect uniformdrying of the hide or skin.

4, That improvement in methods of drying tanned hides and skins whichcomprises, blowing currents of air from one end to the other of eachhide or skin along lines parallel to the backbone line of the hide orskin, and preliminarily restricting the greater portion of the aircurrents to those portions of the hide or skin lying closely adjacent tothe backbone line of each hide or skin.

5. That improvement in methods of drying tanned hides and skins, whichcomprises blowing currents 01' air alternately in diilerent directionsfrom one end to the other of each hide or skin along lines substantiallyparallel to the backbone line of each hide or skin, and, for a certainpart of the time of treatment, substantially restricting the aircurrents to those portions of each hide or skin lying adjacent to thebackbone line thereof.

6. That improvement in methods of drying mineral tanned hides and skinswhich comprises circulating air heated to temperatures above about 2121". in directions substantially parallel to the backbone line of eachhide or skin, and preliminarily restricting currents of air attemperatures of about 245, F. and over for a period of about 40 minutessubstantially to those portions of each hide or skin lying along andadjacent to the backbone line thereof.

7. That improvement in methods of drying mineral tanned hides and skins,which comprises blowing air heated to temeratures within the range ofabout 212 F. to about 250 F. in diilerent directions from one edge toanother of each hide or skin for a period of about 60 minutes, and,during the earlier part of the drying operation, when the airtemperature is highest restricting the currents of air substantially tothose portions of each hide or skin lying along and adjacent to thebackbone line thereon 8. That improvement in methods of drying chrometanned hides and skins which comprises blowing air heated totemperatures within the range of about 220 F. to about 250 F. indiilerent directions from one edge to another of each hide or skin,during the earlier part of the drying operation, restricting thecurrents of air substantially to those portions ofeach hide or skinlying along and adjacent to the backbone line thereof,

and subsequently subjecting all portions of each hide or skin tocurrents of air at temperatures gradually reduced from about 220 F. toabout 70 F. and with the relative humidity of such heated air graduallyreduced to about 30%, so that all'portions of each hide or skin willreceive treatment designed to secure uniform drying effects.

9. That improvement in methods of drying chrome tanned hides and skinswhich comprises subjecting hides or skins to currents of air attemperatures in the range of about 220 F. to about 250 F. and relativehumidity of about 50% to eil'ect removal of moisture from the hides orskins without actual drying thereof, and subsequently subjecting thesesame hides and skins to cooler relatively dry air to complete the dryingoperation.

10. That improvement in methods of drying 'chrome tanned hides and skinswhich comprises circulating air of relative humidity about 50% and of atemperature about 240 F. in directions substantially parallel to thebackbone line of each hide or skin, restricting the currents of air tothose portions of each hide or skin lying along and adjacent to thebackbone line thereof, subsequently subjecting each hide or skin tocurrents of air at temperatures gradually reduced from about 212 F. toabout F. insuch manner that all portions of each hide or skin receivetreatment by such air to secure uniform drying eiIects, and finallysubjecting all portions of each hide or skin to cooler dry currents ofair to effect completion of the drying operation.

11. That improvement in methods of drying tanned hides or skins,following such operations as tanning and coloring in solutions, whichcomprises subjecting them to air of temperatures of 245 F. and over andof high relative humidity, for example, of about 50% and over for a.period of about 40 minutes.

. -HENRY W. HYDE.

DAVID EDGAR.

